U.S. patent application number 13/856719 was filed with the patent office on 2013-10-31 for refractory lining for titanium ore beneficiation.
The applicant listed for this patent is E I DU PONT DE NEMOURS AND COMPANY. Invention is credited to John James BARNES, Peter HILL, Dat NGUYEN, Jay Scott SCHICKLING.
Application Number | 20130287942 13/856719 |
Document ID | / |
Family ID | 42312824 |
Filed Date | 2013-10-31 |
United States Patent
Application |
20130287942 |
Kind Code |
A1 |
BARNES; John James ; et
al. |
October 31, 2013 |
REFRACTORY LINING FOR TITANIUM ORE BENEFICIATION
Abstract
The disclosure relates to a refractory which is resistant to
corrosion which degrades the refractory during titanium-ore
beneficiation in a furnace, particularly a rotary hearth furnace.
In particular, the disclosure relates to a layered refractory
lining for a furnace, for use in a titanium ore beneficiation
process wherein a titanium oxide-rich molten slag is formed,
comprising: (a) a first layer comprising a major proportion of
alumina and a minor proportion of zirconia; (b) a second layer
comprising a resistant agent for the molten slag; wherein the
second layer is between the slag and the first layer.
Inventors: |
BARNES; John James;
(Hockessin, DE) ; NGUYEN; Dat; (Chadds Ford,
PA) ; HILL; Peter; (Woodstown, NJ) ;
SCHICKLING; Jay Scott; (Hendersonville, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E I DU PONT DE NEMOURS AND COMPANY |
Wilmington |
DE |
US |
|
|
Family ID: |
42312824 |
Appl. No.: |
13/856719 |
Filed: |
April 4, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13318614 |
Nov 3, 2011 |
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PCT/US10/33678 |
May 5, 2010 |
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13856719 |
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61175619 |
May 5, 2009 |
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Current U.S.
Class: |
427/230 ;
428/697 |
Current CPC
Class: |
C22B 34/1209 20130101;
F27B 9/16 20130101; C21B 13/006 20130101; C21B 13/105 20130101;
F27D 1/0006 20130101; F27D 1/1684 20130101; C22B 1/02 20130101 |
Class at
Publication: |
427/230 ;
428/697 |
International
Class: |
C22B 1/02 20060101
C22B001/02 |
Claims
1-13. (canceled)
14. A process for forming a resistant agent in a refractory body of
a furnace for use in a titanium ore beneficiation process,
comprising: (i) forming agglomerates comprising carbon-based
materials and a titanium-bearing ore, the quantity of carbon of the
agglomerates being sufficient for, at an elevated temperature,
reducing ferric oxide to ferrous oxide and forming a slag that is
comprised of titanium oxide and iron oxide; (ii) introducing the
agglomerates onto a carbon bed of a moving hearth furnace, wherein
the moving hearth furnace comprises a refractory lining comprising
a first layer comprising alumina and zirconia having about 90 to
about 99 wt. % alumina, and about 1 to about 10 wt. % zirconia,
based on the entire weight of the first layer; (iii) heating the
agglomerates in the moving hearth furnace to a temperature
sufficient for reducing and melting the agglomerates to produce a
titanium oxide-rich molten slag, which contacts the refractory
lining to produce a second layer comprising a resistant agent which
is a reaction product of the slag, the alumina and the zirconia;
wherein the second layer is formed between the slag and the first
layer; and wherein the total amount of calcium oxide, magnesium
oxide, yttrium oxide and cerium oxide is less than 1 wt. %, based
on the total weight of the refractory body.
15. A resistant agent for a titanium oxide-rich molten slag
comprising a reaction product of a first layer of a refractory
lining comprising alumina and zirconia having about 90 to about 99
wt. % alumina, and about 1 to about 10 wt. % zirconia, based on the
entire weight of the first layer and the titanium oxide-rich molten
slag, wherein the resistant agent is the reaction product of the
titanium oxide of the slag and the alumina and zirconia of the
first layer; and wherein the total amount of calcium oxide,
magnesium oxide, yttrium oxide and cerium oxide is less than 1 wt.
%, based on the total weight of the refractory body.
Description
BACKGROUND OF THE DISCLOSURE
[0001] 1. Field of the Disclosure
[0002] The disclosure relates to a layered refractory lining for a
furnace used in the beneficiation of titanium ore. More
particularly, the disclosure relates to a refractory body for
lining a furnace, the refractory body comprising a major proportion
of alumina and a minor proportion of zirconia.
[0003] 2. Description of the Related Art
[0004] Rotary hearth furnaces have been described for the
beneficiation of low grade titanium ores, such as ilmenite, which
contain iron oxide, titanium dioxide, and metal oxide impurities,
into products containing high levels of titanium oxides such as
titanium slag, and metallic iron. However, beneficiating a low
grade ore which contains titanium dioxide and metal oxide
impurities by reduction in a rotary hearth process can pose
processing challenges. In particular, the titanium-rich slags
produced can be highly corrosive to the refractory materials which
are typically used to line the furnace, causing degradation of the
lining, which results in increased production downtime to repair or
replace the refractory.
[0005] Unlike typical ilmenite smelting processes, in which a
freeze lining of the slag acts as a protective barrier between the
refractory and the molten slag, the molten slag in a rotary hearth
process can be in direct contact with the refractory, and therefore
a corrosion-resistant refractory is essential.
SUMMARY OF THE DISCLOSURE
[0006] The disclosure relates to a layered refractory lining for a
furnace, for use in a titanium ore beneficiation process wherein a
titanium oxide-rich and iron oxide-rich molten slag is formed,
comprising:
[0007] (a) a first layer comprising a major proportion of alumina
and a minor proportion of zirconia;
[0008] (b) a second layer comprising a resistant agent reaction
product of the molten slag and the alumina and the zirconia;
wherein the second layer is between the molten slag and the first
layer.
[0009] The second layer can be formed in situ during the
beneficiation process or the second layer can be preformed by
applying to a surface of the first layer a paste comprising a
source of titania, a source of carbon, and a binder to form a
coating thereon, melting the coating to cause a reaction of the
coating with the first layer and form a second layer.
[0010] The furnace can be an electric arc furnace or a rotary
hearth furnace.
[0011] The first layer can comprise alumina and zirconia having
about 90 to about 99 wt. % alumina, and about 1 to about 10 wt. %
zirconia, based on the entire weight of the first layer. More
specifically, the alumina ranges from about 97 wt. % to about 98
wt. % based on the entire weight of the first layer and the
zirconia ranges from about 1 wt. % to about 2 wt. % based on the
entire weight of the first layer. The layered refractory lining can
further comprise calcia and magnesia, yttrium oxide, cerium oxide,
or mixtures thereof.
[0012] In another aspect, the disclosure relates to a process for
forming a resistant agent in a refractory body of a furnace for use
in a titanium ore beneficiation process, comprising:
[0013] (i) forming agglomerates comprising carbon-based materials
and a titanium-bearing ore, the quantity of carbon of the
agglomerates being sufficient for, at an elevated temperature,
reducing ferric oxide to ferrous oxide and forming a slag that is
comprised of titanium oxide and iron oxide;
[0014] (ii) introducing the agglomerates onto a carbon bed of a
moving hearth furnace, wherein the moving hearth furnace comprises
a refractory lining comprising a first layer comprising a major
proportion of alumina and a minor proportion of zirconia;
[0015] (iii) heating the agglomerates in the moving hearth furnace
to a temperature sufficient for reducing and melting the
agglomerates to produce a titanium oxide-rich molten slag, which
contacts the refractory lining to produce a second layer comprising
a resistant agent which is a reaction product of the slag, the
alumina and the zirconia; wherein the second layer is formed
between the slag and the first layer.
[0016] In yet another aspect, the disclosure relates to a resistant
agent for a titanium oxide-rich molten slag comprising a reaction
product of a first layer of a refractory lining comprising a major
proportion of alumina and a minor proportion of zirconia and the
titanium oxide-rich molten slag, the resistant agent being
resistant to degradation, including cracking in the presence of
titanium oxide-rich molten slag. The resistant agent can be the
reaction product of the titanium oxide of the slag and the alumina
and zirconia of the first layer.
[0017] In one embodiment, the disclosure herein can be construed as
excluding any element or process step that does not materially
affect the basic and novel characteristics of the composition or
process. Additionally, the disclosure can be construed as excluding
any element or process step not specified herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a top view of a rotary hearth furnace for the
reduction of titanium-rich ores and production of iron metal and
high grade titanium oxides.
[0019] FIG. 2 is a simplified schematic diagram of the process of
this disclosure.
[0020] FIG. 3 is a photograph of a magnesia-based refractory of
Comparative Example 1.
[0021] FIG. 4 is a photograph of the alumina-based refractory of
Comparative Example 2.
[0022] FIG. 5 is a photograph of the alumina-based refractory of
Comparative Example 3.
[0023] FIG. 6 is a photograph of the alumina-based refractory of
Example 4.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0024] In one of the widely used methods of titanium ore
beneficiation, the ore containing titanium oxides is converted in a
furnace to slag containing higher concentrations of titanium oxides
which can be suitable for use in the production of titanium dioxide
pigment. The disclosure relates to a refractory body for lining at
least a portion of a furnace, more particularly, the refractory
body forms a layered refractory lining, for use in a titanium ore
beneficiation process. For this process, the ore containing
titanium oxides is formed into agglomerates comprising carbon-based
material and the titanium ore. The agglomerates are fed to the
furnace for conversion to slag and other products of reaction. The
quantity of carbon of the agglomerates is sufficient for, at an
elevated temperature, reducing ferric oxide to ferrous oxide and
forming a molten slag comprising titanium oxide and ferrous oxide.
The agglomerates can be fed onto a carbon bed of a moving hearth
furnace.
[0025] A refractory body that is resistant to the corrosive
properties of titanium-rich molten slag is described. The
refractory body comprises a first layer comprising
alumina-zirconia. More particularly, the refractory body comprises
a major proportion of alumina and a minor proportion of zirconia.
The ratio of alumina to zirconia can be represented by the
formula
xAl.sub.2O.sub.3:yZrO.sub.2
wherein x ranges from about 90 to about 99% by weight based on the
total weight of the refractory body, and wherein y ranges from
about 1 to about 10% by weight based on the total weight of the
refractory body. More particularly, x ranges from about 95 to about
99% by weight, based on the total weight of the refractory body,
and wherein y ranges from about 1 to about 5% by weight based on
the total weight of the refractory body. Even more particularly, x
is about 97% to about 98% by weight and y is about 1 to about 2% by
weight based on the total weight of the refractory body. The
refractory body can contain a minor proportion of other compounds
which do not undermine the corrosion resistance property of the
refractory body such as one or more oxides of an alkali metal or an
alkaline earth metal or an oxide of an element of group IVB of the
Periodic Table of the Elements (Sargent-Welch Scientific Company
1979). Some of these compounds may enhance the stability of the
refractory, and thereby contribute to its performance in contact
with the slag. Examples are selected from the group consisting of
calcium oxide, magnesium oxide, yttrium oxide, and cerium oxide and
mixtures thereof. The total amount of these oxides can be less than
1 wt. %, more typically less than 0.5 wt. %, typically from about
0.05 wt. % to about 1 wt. %, even more typically the range is about
0.05 wt. % to about 0.5 wt. %, based on the total weight of the
refractory body.
[0026] In particular, the first layer can be free of silica.
[0027] The refractory body further comprises a second layer
comprising a resistant agent for the slag. The resistant agent can
inhibit corrosion of the refractory body exposed to the
titanium-rich molten slag thus preventing the formation of cracks
in the refractory body. The resistant agent can be a reaction
product of the molten slag, which forms from reduction of the
titanium ore, and the alumina and zirconia of the refractory. The
second layer can also comprise other products of reaction of the
molten slag and the components of the refractory of the first
layer, and, optionally, one or more unreacted components of the
first layer and unreacted slag. The second layer can be formed
during the ore beneficiation process by reaction of the molten slag
with the first layer. More particularly the second layer can be
formed during the ore beneficiation process by reaction of the
components of the first layer and the molten slag. Even more
particularly the second layer can be formed during the ore
beneficiation process by reaction of the alumina and zirconia of
the first layer with the products of reduction of the titanium ore
in the molten slag.
[0028] Alternatively, the second layer can be made in a preforming
step. Preforming of the second layer can be achieved by applying to
the surface of the refractory liner, typically in the rotary hearth
furnace, a paste that is comprised of a source of titania, such as
ilmenite, a source of carbon, such as coal, and a binder suitable
for making a paste of the source of titania and carbon which will
adhere to the first layer and form a coating thereon. The amount
and type of binder will depend on the process conditions but would
be apparent to those skilled in the art of refractories. The
furnace can then be heated to a temperature sufficient to melt the
coating and cause reaction of the coating with the refractory to
form the second layer. Thus, the second layer is formed prior to
the beneficiation and can be considered to be made in a preforming
step. The resistant agent can thus form in the preformed second
layer by reaction of the first layer, more particularly the
components thereof, with the components of the preformed second
layer at an elevated temperature, more particularly at the
temperatures for carrying out the ore beneficiation.
[0029] The refractory body can be in the form of bricks, tiles or a
substantially continuous layer, more particularly a continuous
layer. A commercially available refractory material suitable for
the refractory body is Korrath C98Zr sold by Rath Refractories,
Inc. of Milledgeville, Ga.. The C98Zr refractory contains 97.7 wt.
% alumina, 1.8 wt. % zirconia, 0.2 wt. % (magnesia+calcia), 0.1 wt.
% silica, and 0.2 wt. % alkali metals, based on the entire weight
of the refractory body.
[0030] Typically the furnace can be a moving hearth furnace, more
typically a rotary hearth furnace. However, an electric arc furnace
can also be used.
[0031] Referring to the drawings and more particularly to FIG. 1, a
rotary hearth furnace can be used for reducing the charge. A
furnace 10 can be used having the configuration of a typical
industrial moving hearth furnace. The rotary hearth furnace has a
surface 30 that is rotatable from a material feed zone 12.
[0032] The hearth 30 rotates from the material feed zone through a
plurality of burner zones represented by first burner zone 14,
second burner zone 16, and third burner zone 17. A reaction zone
spans at least a portion of the burner zones. A discharger zone 18
comprises a cooling plate 48 and discharge device 28. The maximum
temperature of the furnace is typically reached in third burner
zone 17. The first and second stages of the process of this
disclosure occur in the reaction zone. The surface 30 is rotatable
in a repetitive manner from the discharge zone 18 to the feed
material zone 12 and through the reaction zone for continuous
operation. The burner zones can each be fired by a plurality of
air/fuel, oxy/fuel, or oxygen enriched burners 22 to produce a
flame 20.
[0033] The material feed zone 12 includes an opening 24 and a feed
mechanism 26 by which the agglomerates are charged to the furnace.
A layer comprising carbon can be located on at least a major
proportion of the surface 30, or the entire surface can comprise a
layer comprising carbon upon which the agglomerates are placed. The
layer comprising carbon can be placed on the surface by any
convenient means, typically by a solid material feeder 34. The
agglomerates can be leveled to a useful height above the surface by
a leveler 29 that spans the width of the surface 30. The
agglomerates are continuously fed to the furnace by the feed
mechanism as the surface is rotated around the furnace and through
each zone. The speed of rotation is controlled by adjusting a
variable speed drive.
[0034] The disclosure also relates to the formation of a resistant
agent for titanium oxide-rich molten slag. In this process,
agglomerates comprising carbon-based material and the titanium ore
are formed, wherein the quantity of carbon of the agglomerates is
sufficient for, at an elevated temperature, reducing ferric oxide
to ferrous oxide and forming a molten slag comprising titanium
oxide and ferrous oxide; introducing the agglomerates onto a carbon
bed of a moving hearth furnace, wherein the moving hearth furnace
comprises a refractory lining comprising a first layer comprising
alumina present in a major proportion and a minor proportion of
zirconia; and heating the agglomerates in the moving hearth furnace
to a temperature sufficient for reducing and melting the
agglomerates to produce a titanium oxide-rich and iron oxide-rich
molten slag and a second layer comprising a resistant agent for the
slag; wherein the second layer forms between the slag and the first
layer.
[0035] A low grade ore containing titanium oxides and iron oxides
can be used. Titanium present in low grade ore occurs in complex
oxides, usually in combination with iron, and also containing
oxides of other metals and alkaline earth elements. Titanium is
commonly found as ilmenites, either as a sand or a hard rock
deposit. Low-grade titanium ores, such as ilmenite sand can contain
from about 45 to about 65 wt. % titanium dioxide, about 30 to about
50 wt. % iron oxides and about 5 to about 10 wt. % gangue, based on
the entire weight of the sand. Rock deposits of ilmenite are
reported to contain from about 45 to about 50 wt. % titanium
dioxide, about 45 to about 50 wt. % iron oxides, and about 5 to
about 10 wt. % gangue, based on the entire weight of the rock
deposit. The process of this disclosure can employ such titanium
ores.
[0036] The agglomerates, useful as the charge to the rotary hearth
process, comprise the ore and a quantity of carbon sufficient for a
first stage melting wherein ferric oxide reduction to ferrous oxide
occurs under reducing conditions. The exact amount of carbon can
vary depending upon the iron oxide content of the ore, and
particularly upon the ferric oxide content. But, less than
stoichiometric quantities of carbon (i.e., quantities of carbon
sufficient to reduce all the iron oxides in the ore to metallic
iron) can be used so that the agglomerates will melt before a
second stage metallizing wherein the majority of the ferrous oxide
reduction to iron metal occurs. A minor degree of such metallizing
can occur in the first stage and is not detrimental to the process
of this disclosure.
[0037] When the amount of carbon is referred to, it means the fixed
carbon content of the material which provides a source of carbon.
Fixed carbon content is determined in the proximate analysis of
solid fuels, such as coal, by heating a sample, in the absence of
air, to 950.degree. C. to remove volatile matter (which typically
includes some carbon). The carbon that remains at 950.degree. C. is
the fixed carbon content.
[0038] For a typical ore that can be used in the process of this
disclosure and containing about 30 to about 50% iron oxides, the
amount of carbon can range from about 0.5 to about 8.0 wt. %, more
typically about 1.0 to about 6.0 wt. % based on the entire weight
of the agglomerate. For ilmenite and/or sand containing ilmenite,
the amount of carbon can range from about 1.0 to about 8.0 wt. %,
more typically about 2.0 to about 6.0 wt. % based on the entire
weight of the agglomerate. For rock deposits of ilmenite, the
amount of carbon can range from about 0.5 to about 5.0 wt. %, more
typically about 1.0 to about 3.0 wt.% based on the entire weight of
the agglomerate.
[0039] Typically, the amount of carbon in the agglomerates is
sufficient for reducing the ferric oxide but insufficient to
metallize more than about 50% of the ferrous oxide, more typically
insufficient to metallize more than about 20% of the ferrous oxide
based on the agglomerate.
[0040] The carbon source useful in the agglomerates can be any
carbonaceous material such as, without being limited to, coal,
coke, charcoal, and petroleum coke.
[0041] Agglomerates can be formed by mixing the ore and the carbon
source, optionally together with a binder material, and shaping the
mixture into pellets, briquettes, extrudates or compacts which are
usually dried at temperatures ranging from about 100.degree. C. to
about 200.degree. C. Equipment capable of mixing and shaping the
feed components are well known to those skilled in the art.
Typically the agglomerates range in average diameter from about 2
to about 4 cm for ease of handling.
[0042] The optional binder material can be, without limitation to,
organic binders or inorganic binders such as bentonite or hydrated
lime. Suitable amounts of binder range from about 0.5 to about 5
wt. %, typically about 1 to about 3 wt. % based on the entire
weight of the agglomerates.
[0043] Unlike some ore reduction processes, the ore of the
agglomerates can be used without being ground into a fine powder.
The ore can, however, be crushed and/or screened, before being
formed into agglomerates, to an average particle size ranging from
about 0.1 to about 1 mm to separate out any large chunks which
might pose handling problems. For example, when rock deposits are
used, they are usually crushed and screened to obtain ore particles
ranging in average size of about 0.1 to about 1 mm.
[0044] The agglomerates can be charged to a rotary hearth furnace
wherein they are heated to a temperature sufficient for the first
stage melting to produce a ferrous oxide-rich molten slag. In a
typical process, the agglomerates can be charged through a feed
chute which deposits them onto a bed of carbonaceous material,
typically a bed of coal or coke particles. The thickness of the bed
can range from about 1 to about 5 cm.
[0045] The temperatures inside the moving hearth furnace sufficient
for the first stage melting can range from about 1300.degree. C. to
about 1800.degree. C., typically from about 1400.degree. C. to
about 1750.degree. C., and more typically from about 1500.degree.
C. to about 1700.degree. C. The particular temperature will depend
on ore composition. The period of time for this melting stage can
range from about 1 minute to about 5 minutes.
[0046] In the first stage melting, the carbon content of the
agglomerates is sufficient to reduce the ferric oxide to ferrous
oxide, but insufficient to complete any substantial metallization
and, additionally, not sufficient for the complete reduction of
ferrous oxide to iron metal.
[0047] The ferrous oxide-rich molten slag which results from the
first stage melting, contacts the carbon bed under reducing
conditions. Through this contact, the ferrous oxide is further
reduced in the second stage metallizing to produce the iron metal
product.
[0048] The temperature inside the moving hearth furnace in the
second stage metallizing is sufficiently high to keep the slag in a
molten state as the ferrous oxide metallization occurs. Suitable
temperatures inside the hearth furnace for this purpose can range
from about 1500.degree. C. to about 1800.degree. C., typically from
about 1600.degree. C. to about 1750.degree. C., and more typically
from about 1600.degree. C. to about 1700.degree. C. The particular
temperature required will vary depending upon ore composition.
[0049] On a large scale furnace, the temperature inside the furnace
in the first stage can be at least about 100.degree. C. lower than
the temperature in the second stage.
[0050] The period of time for this second stage metallizing can be
longer than that for the first stage melting and can range from
about 5 minutes to about 20 minutes. During the first stage,
reduction of ferric oxide in the presence of the carbon contained
in the agglomerates and melting occur rapidly. In contrast, in the
second stage, allowing sufficient time for the ferrous oxide-rich
molten slag to flow over the carbon bed during the metallization
can enhance production of large metal particles since the iron
droplets of the molten slag will coalesce into larger droplets
which maintain their size during cooling to form solid metal
particles.
[0051] As the second stage metallization proceeds, the slag becomes
less fluid and the titanium concentration of the slag increases.
The conditions sufficient for maintaining slag fluidity can help
the iron droplets in the molten slag to coalesce which facilitates
the formation of the easily separable large particles of iron.
[0052] The slag solidifies as the metallization approaches
completion. Preferably, the metallization is carried out until at
least about 90% completion, based on the agglomerates, even more
preferably until at least about 95% completion. The iron metal
which can be in the form of large granules is readily separable
from the solid slag by cost effective processes. Mechanical
processes are ideally used for separating the iron metal. Chemical
processes such as chemical leaching are not needed. Additionally
extensive mechanical separation processes such as intensive
grinding are not needed.
[0053] Typical methods for separating the metal include crushing,
grinding, screening and magnetic separation.
[0054] Typically the iron granules of the process range in average
diameter from about 0.05 to about 10 mm, and more typically from
about 0.1 to about 5 mm.
[0055] Typically, the solid slag product of the process comprises
greater than about 85% titanium oxides, and more typically greater
than about 87% titanium oxides, based on the entire weight of the
solid slag product, after separation of the mechanically separable
metallic iron. The term "titanium oxides" means TiO.sub.2,
Ti.sub.3O.sub.5, and Ti.sub.2O.sub.3. The solid slag product can
also contain smaller amounts of titanium in the form of TiO, TiC,
and TiN. The solid slag product can contain a minor amount of
residual metallic iron. The residual metallic iron is usually the
portion of metallic iron particles below about 50 microns in
diameter. Usually the amount of residual metallic iron is less than
about 6%, more typically less than about 4% based on the entire
weight of the solid slag product, after mechanical separation of
the mechanically separable metallic iron granules. There can be
other small amounts of impurities such as FeO, and other oxides.
The amount of these other impurities is usually less than 8% and
more typically less than 6% of the entire weight of the solid slag
product.
[0056] The moving hearth furnace can be any furnace which is
capable of exposing the agglomerates to at least two high
temperature zones on a bed of carbon. A suitable furnace can be a
tunnel furnace, a tube furnace or a rotary hearth furnace. The
process can employ a single furnace structure.
[0057] Referring to FIG. 2, the process is shown whereby the ore is
introduced to the mixing zone 51. The carbon can be introduced to a
size reduction zone 50 prior to introduction to the mixing zone 51
wherein the ore and the carbon together with any optional
additives, such as binders, are mixed together and formed into
agglomerates. The agglomerates are introduced to rotary hearth
furnace zone 52 wherein the ferric oxide of the agglomerates is
reduced and metallized as described herein. The hot product 42 as
shown in FIG. 2 is cooled by any convenient means. The cooled
product is then screened in the screening zone 53, then ground in
grinding zone 54 to separate the iron metal from the high grade
titanium oxides product. Recycle material can also be separated and
introduced to the mixing zone 51. The iron metal product can be
formed into briquettes in briquetting zone 55 from which the iron
metal product is withdrawn.
[0058] In one embodiment, the disclosure herein can be construed as
excluding any element or process step that does not materially
affect the basic and novel characteristics of the composition or
process. Additionally, the invention can be construed as excluding
any element or process step not specified herein.
[0059] Applicants specifically incorporate the entire content of
all cited references in this disclosure. Further, when an amount,
concentration, or other value or parameter is given as either a
range, preferred range, or a list of upper preferable values and
lower preferable values, this is to be understood as specifically
disclosing all ranges formed from any pair of any upper range limit
or preferred value and any lower range limit or preferred value,
regardless of whether ranges are separately disclosed. Where a
range of numerical values is recited herein, unless otherwise
stated, the range is intended to include the endpoints thereof, and
all integers and fractions within the range. It is not intended
that the scope of the invention be limited to the specific values
recited when defining a range.
EXAMPLES
[0060] The following Examples illustrate the present disclosure.
All parts, percentages and proportions are by weight unless
otherwise indicated.
Comparative Example 1
[0061] In this Example, a refractory containing 92 wt. % magnesia,
6 wt. % alumina, 1 wt. % silica, and 1 wt. % calcia, based on the
entire weight of the refractory (Magnel H F sold by ANH
Refractories of Moon Township, Pa.) was used. A cavity having a
depth of 15 mm was drilled into a 50 mm wide.times.50 mm
long.times.40 mm tall refractory brick to form a cup. A mixture
consisting of 92.5 wt. % ilmenite titanium-bearing ore (containing
about 60 wt % TiO2, based on the entire weight of the ore), 5.5 wt.
% bituminous coal, and 2 wt. % binder, based on the entire weight
of the mixture was shaped into pellets and dried at a temperature
of about 110.degree. C. The dried pellets were about 20 mm in
diameter. Such a pellet was placed into the cup, which contains a
thin layer of a carbon-based material, which may include certain
bituminous or anthracite coals, metallurgical cokes, and petroleum
cokes, including sponge coke, needle coke, shot coke, and fluid
coke and the cup was placed in a box furnace and heated to
1700.degree. C. for 15 minutes, during which time the generation of
a titanium-rich slag inside the cavity of the cup was observed. The
temperature was then increased to 1735.degree. C. for a period of 4
hours. The cup was removed from the furnace, and allowed to cool.
FIG. 3 is a photograph of a cross-section of the cup showing slag
penetration into the refractory and cracking of the cup. The
extensive cracking indicated that the refractory composition was
unable to resist damage from the titania-rich slag. The cup was
examined using optical microscopy and scanning electron
microscopy/electron dispersive spectroscopy which revealed that the
magnesium oxide phase in the refractory reacted with the slag,
resulting in the transformation to phases that contain titanium and
iron, in addition to magnesium. Cracking was evident in the
microstructure of the refractory, caused by the transformation of
magnesium oxide.
Comparative Example 2
[0062] This Example followed the same procedure as Comparative
Example 1, except the refractory used contained 90 wt. % alumina,
9.2 wt. % silica, 0.1 wt. % Fe.sub.2O.sub.3, 0.1% TiO.sub.2, 0.1
wt. % (CaO+MgO), 0.2 wt. % alkali metals. The remainder (0.3 wt. %)
was not specified by the manufacturer, all based on the entire
weight of the refractory (Korrath C90 sold by Rath Refractories,
Inc. of Milledgeville, Ga.).
[0063] FIG. 4 is a photograph of a cross-section of the cup showing
extensive slag penetration into the refractory and cracking of the
cup, even into the sidewalls of the cup. The extensive cracking
indicated that the refractory composition was unable to resist
damage from the titania-rich molten slag that formed during the
reduction process.
Comparative Example 3
[0064] This Example followed the same procedure as Comparative
Example 1, except a refractory containing 99.6 wt. % alumina, 0.07
wt. % SiO.sub.2, 0.05 wt. % Fe.sub.2O.sub.3, 0.03 wt. % TiO.sub.2,
0.1 wt. % (CaO+MgO), 0.1 wt. % (Na.sub.2O+K.sub.2O), based on the
entire weight of the refractory was used. The remainder (0.05%) was
not specified by the manufacturer, Rath Refractories, Inc. of
Milledgeville, Ga.
[0065] Examination of the cup revealed that the slag penetrated the
refractory and formed a product layer. The cup also had extensive
cracking including at the interface between the areas penetrated by
the slag and areas that were not penetrated by the slag. The
extensive cracking indicated that the refractory composition was
unable to resist damage from the titania-rich molten slag that
formed during the reduction process. FIG. 5 is a photograph of a
cross-section of the cup showing the damage to the cup resulting
from the process.
Example 4
[0066] This Example followed the same procedure as Comparative
Example 1 except a refractory containing 97.7 wt. % alumina, 1.8
wt. % zirconia, 0.2 wt. % (magnesia+calcia), 0.1 wt. % silica, and
0.2 wt. % alkali metals, based on the entire weight of the
refractory body, was used. FIG. 6 is a photograph of a
cross-section of the cup showing that the slag had penetrated into
the refractory and formed a product layer but no evidence of cracks
in the cup was observed.
[0067] Examination of the cup using optical microscopy and scanning
electron microscopy/electron dispersive spectroscopy revealed no
evidence of cracking on a microscopic scale. Examination of the
chemical composition of the product layer that formed in the cup
revealed aluminum titanate, the presence of zirconia, unreacted
refractory material, and unreacted slag. The lack of cracking
indicated that the refractory composition was capable of resisting
damage from exposure to the high temperatures of the furnace and
the titania-rich molten slag that formed during the reduction
process.
[0068] The description of illustrative and preferred embodiments of
the present disclosure is not intended to limit the scope of the
disclosure. Various modifications, alternative constructions and
equivalents may be employed without departing from the true spirit
and scope of the appended claims.
* * * * *